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Friday, July 6, 2012

PowerPoint Presentation On Biofilms and Quorum Sensing

PPT On Biofilms and Quorum Sensing

Presentation Transcript:
1. Biofilms and Quorum Sensing

2. Biofilms
Biofilms are organised microbial systems consisting of cells associated with surfaces - Likely the most wide-spread mode of growth for bacteria in nature

3. Biofilms In the natural world most bacteria aggregate as biofilms -
they form when bacteria adhere to surfaces in aqueous environments and begin to excrete a polysaccharide that can anchor them to all kinds of material. The biofilm is held together and protected by the polysaccharide matrix. This matrix protects the cells within it and facilitates communication among them through biochemical signals. Bacteria living in a biofilm usually have significantly different properties from free-floating bacteria of the same species, as the dense and protected environment of the film allows them to cooperate and interact in various ways.

4. Biofilms
A biofilm can be formed by a single bacterial species, but more often biofilms consist of many species of bacteria, as well as fungi, algae, protozoa, debris and corrosion products. Once anchored to a surface, biofilm microorganisms carry out a variety of detrimental or beneficial reactions (by human standards), depending on the surrounding environmental conditions.

 5. Advantages for Bacteria
♦ Creation of habitable niches
♦ Protection against: - Physical forces (e.g. in flowing systems) - Phagocytosis by immune cells - Grazers (e.g. ciliates, amoeba) - Viruses
♦ Barrier against toxic substances
♦ Facilitates intercellular communication
♦ Close proximity of cells enables genetic exchange

6. Disadvantages for mankind:
♦ Immune system can not attack biofilms
♦ Antibiotics/antimicrobial agents fail
♦ Slow the flow of liquids or clog pipelines
♦ Accelerate corrosion of pipelines
♦ Risk for drinking water supply via pipes

7. Effects of Biofilms
Microbial biofilms on surfaces result in billions of dollars in losses yearly due to equipment damage, product contamination, energy losses and medical infections. Conventional methods of killing bacteria (such as antibiotics, and disinfection) are often ineffective with biofilm bacteria. The huge doses of antimicrobials required to rid systems of biofilm bacteria are environmentally undesirable  and medically impractical. Conversely, microbial processes at surfaces also offer opportunities for positive industrial and environmental effects, such as bioremediating hazardous waste sites, biofiltering industrial water, and forming biobarriers to protect soil and groundwater from contamination. 

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PowerPoint Presentation On Plants in response to stress

PPT On Plants in response to stress

Presentation Transcript:
1. Plants in response to stress

2. introduction
Stress is any change in environmental conditions. External conditions that adversely affect growth, development, or productivity. Stresses trigger a wide range of plant responses: altered gene expression cellular metabolism changes in growth rates and crop yields

3. Types of stress Biotic
- imposed by other organisms. Abiotic - arising from an excess or deficit in the physical or chemical environment. Biotic and abiotic stresses can reduce average plant productivity by 65% to 87%, depending on the crop. Resistance or sensitivity of plants to stress depends on: the species the genotype development age

4. Environmental conditions
 that can cause stress water-logging Drought high or low temperatures excessive soil salinity inadequate mineral in the soil too much or too little light

5. Stress resistance mechanisms
 Avoidance mechanisms prevents exposure to stress Tolerance mechanisms permit the plant to withstand stress Acclimation alter their physiology in response stress

6. Leucaena leucocephala
Tropical leguminous tree. Grows better in soil having basic pH . Used in wood production, soil improvement, reforestration, for fodder purposes. Tolerant to salinity and non-tolerant to water logging. Known to be significantly affected in response to external salt content( NaCl).

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PowerPoint Presentation On Control of Microbial Growth

PPT On Control of Microbial Growth

Presentation Transcript:
1. Control of Microbial Growth

2. Control of Microbial Growth:
Introduction Early civilizations practiced salting, smoking, pickling, drying, and exposure of food and clothing to sunlight to control microbial growth. Use of spices in cooking was to mask taste of spoiled food. Some spices prevented spoilage. In mid 1800s Semmelweiss and Lister helped developed aseptic techniques to prevent contamination of surgical wounds. Before then: Nosocomial infections caused death in 10% of surgeries. Up to 25% mothers delivering in hospitals died due to infection

3. Control of Microbial Growth:
Definitions Sterilization: Killing or removing all forms of microbial life (including endospores) in a material or an object. Heating is the most commonly used method of sterilization. Commercial Sterilization: Heat treatment that kills endospores of Clostridium botulinum the causative agent of botulism, in canned food. Does not kill endospores of thermophiles, which are not pathogens and may grow at temperatures above 45oC.

 4. Control of Microbial Growth:
Definitions Disinfection: Reducing the number of pathogenic microorganisms to the point where they no longer cause diseases. Usually involves the removal of vegetative or non-endospore forming pathogens. May use physical or chemical methods. Disinfectant: Applied to inanimate objects. Antiseptic: Applied to living tissue (antisepsis). Degerming: Mechanical removal of most microbes in a limited area. Example: Alcohol swab on skin. Sanitization: Use of chemical agent on food-handling equipment to meet public health standards and minimize chances of disease transmission. E.g: Hot soap & water.

5. Control of Microbial Growth:
Definitions Sepsis: Comes from Greek for decay or putrid. Indicates bacterial contamination. Asepsis: Absence of significant contamination. Aseptic techniques are used to prevent contamination of surgical instruments, medical personnel, and the patient during surgery. Aseptic techniques are also used to prevent bacterial contamination in food industry.

6. Control of Microbial Growth:
Definitions Sepsis: Comes from Greek for decay or putrid. Indicates bacterial contamination. Asepsis: Absence of significant contamination. Aseptic techniques are used to prevent contamination of surgical instruments, medical personnel, and the patient during surgery. Aseptic techniques are also used to prevent bacterial contamination in food industry.

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PowerPoint Presentation On Pedigree Analysis

PPT On Pedigree Analysis


Presentation Transcript:
1. Pedigree Analysis

2. Why do Pedigrees?
Punnett squares and chi-square tests work well for organisms that have large numbers of offspring and controlled matings, but humans are quite different: 1. small families. Even large human families have 20 or fewer children. 2. Uncontrolled matings, often with heterozygotes. 3. Failure to truthfully identify parentage.

3. Goals of Pedigree Analysis
1. Determine the mode of inheritance: dominant, recessive, partial dominance, sex-linked, autosomal, mitochondrial, maternal effect. 2. Determine the probability of an affected offspring for a given cross.

4. Y-Linked Inheritance
We will now look at how various kinds of traits are inherited from a pedigree point of view. Traits on the Y chromosome are only found in males, never in females. The father’s traits are passed to all sons. Dominance is irrelevant: there is only 1 copy of each Y-linked gene (hemizygous).

5. Mitochondrial Genes
Mitochondria are only inherited from the mother. If a female has a mitochondrial trait, all of her offspring inherit it. If a male has a mitochondrial trait, none of his offspring inherit it. Note that only 1 allele is present in each individual, so dominance is not an issue.

6. Outsider Rules
In any pedigree there are people whose parents are unknown. These people are called “outsiders”, and we need to make some assumptions about their genotypes. Sometimes the assumptions are proved wrong when the outsiders have children. Also, a given problem might specify the genotype of an outsider. Outsider rule for dominant pedigrees: affected outsiders are assumed to be heterozygotes. Outsider rule for recessive pedigrees: unaffected (normal) outsiders are assumed to be homozygotes. Both of these rules are derived from the observation that mutant alleles are rare.

7. Maternal Effect Genes
The maternal effect rule: “Mother’s genotype determines offspring’s phenotype.” Assume that the trait is recessive, in a complete dominance situation. Also assume all “outsiders” (people with unknown parents) are homozygous for the allele they are expressing : the dominant allele if they are unaffected, and the recessive allele if they are affected.

 8. Sex-Influenced Trait
Assume that the trait is dominant in males but recessive in females. Assume all outsiders are homozygotes. Thus: DD is always affected dd is always normal Dd is affected in males, but normal in females

9. Sex-Limited Trait
There are several possibilities for dominance, but for this problem assume the trait is dominant but only expressed in males. Affected outsider males are heterozygous; unaffected males are homozygous normal Assume that outsider females are homozygous normal.

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